全文获取类型
收费全文 | 10473篇 |
免费 | 42篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 14篇 |
综合类 | 5篇 |
化学工业 | 279篇 |
金属工艺 | 33篇 |
机械仪表 | 24篇 |
建筑科学 | 82篇 |
矿业工程 | 14篇 |
能源动力 | 59篇 |
轻工业 | 148篇 |
水利工程 | 17篇 |
石油天然气 | 18篇 |
武器工业 | 4篇 |
无线电 | 261篇 |
一般工业技术 | 284篇 |
冶金工业 | 8952篇 |
原子能技术 | 27篇 |
自动化技术 | 297篇 |
出版年
2021年 | 18篇 |
2019年 | 14篇 |
2018年 | 24篇 |
2017年 | 15篇 |
2016年 | 27篇 |
2015年 | 21篇 |
2014年 | 30篇 |
2013年 | 107篇 |
2012年 | 46篇 |
2011年 | 76篇 |
2010年 | 42篇 |
2009年 | 47篇 |
2008年 | 71篇 |
2007年 | 65篇 |
2006年 | 65篇 |
2005年 | 55篇 |
2004年 | 47篇 |
2003年 | 57篇 |
2002年 | 44篇 |
2001年 | 34篇 |
2000年 | 45篇 |
1999年 | 332篇 |
1998年 | 2840篇 |
1997年 | 1588篇 |
1996年 | 1045篇 |
1995年 | 596篇 |
1994年 | 481篇 |
1993年 | 587篇 |
1992年 | 98篇 |
1991年 | 126篇 |
1990年 | 142篇 |
1989年 | 124篇 |
1988年 | 121篇 |
1987年 | 115篇 |
1986年 | 116篇 |
1985年 | 94篇 |
1984年 | 34篇 |
1983年 | 34篇 |
1982年 | 52篇 |
1981年 | 54篇 |
1980年 | 100篇 |
1979年 | 20篇 |
1978年 | 32篇 |
1977年 | 209篇 |
1976年 | 472篇 |
1975年 | 25篇 |
1974年 | 11篇 |
1973年 | 21篇 |
1971年 | 14篇 |
1970年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
The purpose of the study was to identify psychiatric symptoms, neurological impairments, and situational factors associated with the emergence of violence and with its persistence. Psychiatric symptoms were assessed in newly admitted physically assaultive psychiatric patients and nonviolent controls. Patients were than evaluated for 4 weeks to determine the persistence or resolution of these physical assaults. Patients who showed marked resolution of assaults were classified as transiently violent (n = 41), and those who remained assaultive throughout were categorized as persistently violent (n = 34). At the end of 4 weeks, all patients received a comprehensive psychiatric and neurological assessment. Physical assaults were associated initially with prominent positive psychotic symptoms. Both transiently and persistently violent patients were more psychotic than the nonviolent controls; however transiently violent patients showed better resolution of these symptoms over the 4 weeks. They also evidenced less frontal lobe impairment on the neurological examination than the persistently violent patients. The two violent groups differed in their susceptibility to environmental influences: the surrounding ward agitation fostered physical assaults in transiently but not in persistently violent patients. This differentiation between transiently and persistently violent patients has major implications for the comprehensive treatment of violent behavior. 相似文献
112.
JA Walker-Smith 《Canadian Metallurgical Quarterly》1997,11(3):593-610
The aim of therapy in Crohn's disease in childhood is to induce and to maintain a remission of disease activity so that normal growth and development of the child may occur. Enteral nutrition may now be recommended as the first-line treatment for most children with Crohn's disease. However, the evidence for remission is better for children with Crohn's disease of the small intestine rather than of the large intestine. There is evidence that amino acid feeds (elemental), whole protein (polymeric) and protein hydrolysate feeds (semi-elemental) may all be successful. Such a therapeutic approach can lead to healing of the mucosa and down-regulation of inflammation. However, in some cases surgery is required, particularly in children with growth failure and delayed puberty. Drug therapy also continues to have a role in therapy especially with severe colonic disease. 相似文献
113.
114.
MT Massie MJ Rohrer JA Leppo BS Cutler 《Canadian Metallurgical Quarterly》1997,25(6):975-82; discussion 982-3
PURPOSE: Because dipyridamole thallium (DT) scanning is a useful predictor of perioperative cardiac events, a positive results of a DT scan is frequently the basis for performing more invasive cardiac evaluation and for consideration for performing coronary revascularization procedures before performing peripheral vascular surgery. The rationale for this approach has been that the treatment of anatomically significant coronary artery disease would lower the risk of performing a subsequent vascular operation. However, the benefit of performing aggressive diagnostic and therapeutic cardiac procedures in such patients remains unproved. To examine this issue, data from patients who underwent coronary angiography because of thallium redistribution were compared with data from matched control subjects who underwent peripheral vascular operations without further cardiac evaluation. METHODS: The medical records of 70 consecutive patients who underwent coronary angiography because of the presence of two or more segments of redistribution on DT scan were reviewed and compared with 70 other patients matched with respect to age, gender, peripheral vascular operation, and number of segments of redistribution on DT scan who did not undergo additional cardiac evaluation. RESULTS: DT scans were performed on 934 preoperative peripheral vascular surgery patients to help in the assessment of operative risk. Ischemic responses, defined as two or more segments of redistribution, were observed in 297. Of these, 70 underwent cardiac catheterization and 25 underwent coronary revascularization procedures. Adverse outcomes affected 46% of the coronary angiography group and 44% of the control group (p = NS). Patients who underwent coronary angiography and were considered for myocardial revascularization had fewer cardiac events with a subsequent vascular operation than did the control subjects. However, any possible benefit from invasive cardiac evaluation was offset by the three deaths and two myocardial infarctions (MIs) that complicated the cardiac evaluation. There was no significant difference between the angiography group and the matched control subjects with respect to perioperative nonfatal MI (13% vs 9%), fatal MI (4% vs 3%), late nonfatal MI (16% vs 19%), or late cardiac death (10% vs 13%). In long-term follow-up, MIs occurred later in patients who underwent coronary angiography than the control subjects (p = 0.049), but this difference was not associated with an improvement in the overall survival rate. CONCLUSIONS: The risks of extended cardiac evaluation and treatment did not produce any improvement in either the perioperative or the long-term survival rate. For most vascular surgery patients who have a positive result of a DT scan, coronary angiography does not provide any additional useful information. 相似文献
115.
Two-dimensional map of Haemophilus influenzae following protein enrichment by heparin chromatography
M Fountoulakis H Langen S Evers C Gray B Takács 《Canadian Metallurgical Quarterly》1997,18(7):1193-1202
Two-dimensional gel electrophoresis separates several hundred protein molecules in one single experiment and is efficiently used to study the products expressed by different genomes. Low-copy-number gene products are invisible on a stained two-dimensional map and must be enriched such that sufficient amounts are present for visualization and identification. We investigated the enrichment of proteins of the bacterium Haemophilus influenzae by chromatography on immobilized heparin which has affinity for growth and protein biosynthesis factors. Total soluble proteins of the microorganism were fractionated on Heparin-Actigel which resulted in enrichment of approximately 160 proteins. The eluates, representing about 40% of the applied proteins, were analyzed by two-dimensional gel electrophoresis and the protein spots were characterized by amino acid composition analysis and matrix-assisted laser desorption ionization mass spectrometry. The proteins enriched by chromatography on the heparin gel were not exclusively low-copy-number gene products and they did not exclusively belong to one single class of proteins. The proteins that bound to the heparin gel are indicated in a two-dimensional protein map which includes more than 110 newly identified proteins. 相似文献
116.
M Korbonits PJ Trainer JA Little R Edwards PG Kopelman GM Besser F Svec AB Grossman 《Canadian Metallurgical Quarterly》1997,46(6):751-757
Modern liver surgery is based upon deep knowledge of the surgical anatomy of the liver and improvements with ultrasounds imaging techniques have provided multidimensional interpretations of the liver anatomy intraoperatively. The technical advances with real-time scanning combined with the pioneering efforts of the Japanese liver surgeons have permitted the dynamic adaptation of the functional liver anatomy to the real anatomy, thus intimately aiding in segment oriented anatomical resection. Intraoperative ultrasound afford several advantages such as viewing the internal anatomy in direct relationship to the surface landmarks under the probe, enabling higher frequencies resulting in greater image resolution. The utilization of intraoperative ultrasound can modify the tactics involved with resection of both primary and metastatic liver tumours. The routine use of intraoperative ultrasound is strongly advocated since more complex procedures can be performed safely since the surgeon proceeds with complete knowledge of the real liver anatomy when deciding the feasibility and extent of liver resection. 相似文献
117.
Examines, in the context of cancer illness, S. E. Taylor and J. D. Brown's (see record 1988-16903-001) claim that mental health is to a degree predicated on illusory beliefs about the self, one's control, and the future. The Heroic Model (HM), a stance toward cancer characterized by belief that positive thoughts and feelings, a fighting spirit, and an optimistic outlook will promote cancer remission, is presented as paradigmatic of Taylor and Brown's thesis. Strong and weak formulations of the HM (the former affirming a direct influence of mental states over physical processes, and the latter affirming indirect effects only) are examined with respect to their potential adaptive value as true or false beliefs, with different consequences for well-being. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
118.
119.
DA Gray 《Canadian Metallurgical Quarterly》1997,54(6):1553-1562
This study demonstrates that invertebrate acoustic signals can provide information about male phenotypic attributes, and that females can use this acoustic information in mate choice to select a phenotypically superior mate. I investigated the relationships between a male acoustic sexual signal, the phenotype of the signaller, and the female response to signal variation. I recorded and analysed the calling songs of male house crickets, Acheta domesticus. The analyses showed that chirps convey information about male size. With the exception of amplitude, the mean number of pulses per chirp was the best predictor of male size. I performed a laboratory tape-playback experiment to determine female preference during phonotaxis. Females preferred tapes playing the chirps of large males, specifically chirps with a greater number of pulses per chirp. Selection on the female preference is discussed.Copyright 1997 The Association for the Study of Animal Behaviour 相似文献
120.
Tempest Philip R.; White Patricia; Williamson E.Diane; Titball Richard W.; Kelly David C.; Kemp Graham J.L.; Gray Peter M.D.; Forster Simon J.; Carr Frank J.; Harris William J. 《Protein engineering, design & selection : PEDS》1994,7(12):1501-1507
We have used the technique of antibody reshaping to producea humanized antibody specific for the a toxin of Clostridiumperfringens. The starting antibody was from a mouse hybridomafrom which variable (V) region nucleo-tide sequences were determined.The complementarity-determining regions (CDRs) from these Vregions were then inserted into human heavy and light chainV region genes with human constant region gene fragments subsequentlyadded. The insertion of CDRs alone into human frameworks didnot produce a functional reshaped antibody and modificationsto the V region framework were required. With minor frameworkmodifications, the affinity of the original murine mAb was restoredand even exceeded. Where affinity was increased, an alteredbinding profile to overlapping peptides was observed. Computermodelling of the reshaped heavy chain V regions suggested thatamino acids adjacent to CDRs can either contribute to, or distort,CDR loop conformation and must be adjusted to achieve high bindingaffinity. 相似文献